1. Field of the Invention
The present invention relates to an ink jet recording apparatus with a recovering device for recovering poor ink jetting condition of an ink jet head into good ink jetting condition thereof. In particular, the present invention relates to an ink jet recording apparatus through which it can avoid that the ink shifted from the ink jet head to a cap installed in the recovering device is leaked from the cap while recovering operation.
2. Description of Related Art
In general, an ink jet recording apparatus is used for recording images, characters, figures, etc. on a recording medium such as a print sheet by ejecting ink droplets from an ink jet head. In this ink jet recording apparatus, it will occur in the ink jet head a condition where ink droplets cannot be ejected therefrom or where ink droplets cannot be correctly ejected therefrom. These conditions will occur due to that dust (which may be paper powders from the print sheet) adheres to a nozzle plane of the ink jet head, air bubbles are produced in the ink in the ink jet head by sucking of air from top face of the nozzle plane or viscosity of the ink in ink paths of the nozzles becomes high by evaporation of water in the ink.
Thus, there will be necessary recovering operation to improve the above inferior ink jetting conditions of the ink jet head to good ink jetting condition. As the recovering operation, in the conventional ink jet recording apparatus, following operation is generally conducted. That is, the nozzle plane of the ink jet head is covered by the cap when a carriage mounting the ink jet head comes to a predetermined position, and the dust on the nozzle plane or the inferior ink with air bubbles or high viscosity is sucked and removed by purge operation through which it is produced a negative pressure in the paths of the nozzles through the cap. This purge operation is divided into two stages. In the first stage, it is conducted a first suction operation (main suction operation) where the nozzle plane of the ink jet head is sucked under a state that the nozzle plane is completely sealed by the cap and the ink in the nozzles is sifted in the cap. And thereafter in the second stage, it is conducted a second suction operation (secondary suction operation) where the nozzle plane of the ink jet head is sucked under a state that a small gap is formed between the nozzle plane and the cap and the ink gathered in the cap is shifted to a drain tank.
It is disclosed in Japanese Patent Application, laid open No. Hei 6-126,947, an ink jet recording apparatus in which the purge operation similar to the above is conducted. In the disclosed ink jet recording apparatus, further the third suction operation is done after the second suction operation. That is, in such ink jet recording apparatus, the nozzle plane of the ink jet head is sucked while the second suction operation under a state that the nozzle plane and the cap are partially sealed and opened, and thereafter the nozzle plane is sucked while the third suction operation under a state that the nozzle plane and the cap are fully separated. Thereby, the ink gathered in the cap can be reliably removed therefrom without raising its cost.
However, in the above conventional ink jet recording apparatus, there is a problem that leak of the ink from the cap cannot be fully avoided while the secondary suction operation, as follows. In this ink jet recording apparatus, a suction pump is once stopped after the first suction operation and the negative pressure produced during the first suction operation varnishes. Thereafter, the cap is slightly separated from the ink jet head and both the cap and the ink jet head is held in the state that both are partially sealed and opened. Therefore, since the negative pressure of the suction pump does not act in the cap until the second suction operation is done by again operating the suction pump after the above state is realized, the ink is leaked from the gap formed between the nozzle plane and the cap. Further, the leaked ink is adhered onto the various parts of the ink jet recording apparatus and the recording medium, as a result, the inner parts of the apparatus and the recording medium becomes dirty by the leaked ink.
Here, in case that the cap is slightly separated from the ink jet head while the suction pump is held to operate after the first suction operation, air is instantaneously flowed in the cap that the negative pressure acts, thereby impact force occurs in the cap due to abrupt pressure change therein. Thus, it is necessary to avoid the above condition that the cap is separated from the ink jet head while the suction pump is held to operate. Concretely to say, meniscus (air-liquid interface) of the ink in the nozzles is destroyed and air is deeply enters in the ink jet head through the nozzles. In this case, the inferior ink jetting condition of the ink jet head is instead promoted more and more.